The present invention relates to an apparatus for testing the ability of a filter to filter contaminants, and more particularly to an apparatus for automatically testing the ability of filters to filter solid contaminants from a fluid.
Many machines circulate oil for lubricating moving parts or use hydraulic fluid to transmit power or control signals. All of these machines use filters to remove contaminants from the fluid circulated in order to maintain their performance, reliability and desired longevity. The filters maintain the size and count of solid contaminant particles below specified limits. In order to determine if a filter can function as intended it is necessary to define and evaluate its performance. The performance of filters is tested both to predict the performance of the filter in its actual operation and to compare the performance of filters of different design, construction and characteristics.
The ability of a filter to remove contaminants is the subject of various standards, such as ISO 16889. While the test systems called for in these specifications generally perform adequately, there is a need for a more accurate, more automated, more flexible and user friendly test system. Such a test system should be able to conduct tests of both single pass filtration efficiency and multi-pass filtration efficiency. Single pass filtration efficiency is the particle removal efficiency of a filter in applications where the fluid passes the filter only once and is not returned for repeated passes through the filter (e.g., fuel filters and reservoir filling filters). Multipass filtration efficiency is the particle removal efficiency of a filter in applications in which the same fluid continuously recirculates through the filter (e.g., hydraulic or lubricating systems). A comprehensive filter test should be able to evaluate filter performance based on some or all of the following parameters:
Particulate Removal Efficiency (i.e., the effectiveness of the filter expressed as the percentage of the number of particles in specific size ranges removed from the flow of fluid passing through the filter) based on the Filtration Ratio (i.e., the number of particles in a specific size range entering the filter, divided by the number of particles in the same size range exiting the filter);
Filter Life based on the Apparent Contaminant Capacity (i.e., the quantity of contaminant injected into a filter causing the differential pressure across the filter to rise to a specific value);
Pressure Loss based on the Flow/Differential pressure relationship; and
Structural Integrity based on the maximum differential pressure the filter is capable of withstanding without loss of filtration efficiency.
The present invention is embodied in a test system for automatically testing a fluid filter or other hydraulic component or system according to one or more test parameters. The test system is positioned at a first location and includes a test fluid path having substantially a closed loop path through the hydraulic component under test and a controller, capable of receiving one or more operational parameters associated with the hydraulic component test system, that monitors one or more of the operational parameters, controls the operation of the test system and calculates and reports the results of a test conducted by the hydraulic component test system. The controller includes memory that stores data related to the operational parameters monitored by the controller during the course of a test and capable of storing a test program, and a test program, stored in the memory, that includes one or more test parameters specifying how the test is to be conducted, for operating the controller in the course of the test. The test system also includes the following: a local input device operably connected to the controller and configured to convey to the test program one or more test parameters; a test fixture that houses the hydraulic component to be tested, the test fixture including inlet and outlet connections in fluid communication with the test fluid path; a main fluid reservoir system, operably connected to and controlled by the controller and capable of containing a supply of fluid that is substantially free of contaminants before a test is commenced, and including a main fluid reservoir tank having a fluid inlet and a fluid outlet, the inlet and outlet each in fluid communication with the test fluid path; a contaminant injection system capable of containing a supply of contaminated fluid, that includes at least one contaminant tank, each tank capable of containing a supply of contaminated fluid and having a fluid outlet in fluid communication with the test fluid path upstream of the test fixture, for introducing contaminants into the fluid flowing into the test component, and a contaminant fluid flow control device, operably connected to and controlled by the controller and in fluid communication with and positioned between each contaminant tank outlet and the test fluid path, that controls the flow of fluid from each contaminant tank into the test fluid path upstream of the test fixture; a contaminant monitoring system that includes an upstream contaminant monitor, operably connected to and controlled by the controller and in fluid communication with the test fluid path at a position near the inlet of the test fixture, that monitors the contaminant level of fluid in the test fluid path upstream of the test fixture and reports the monitored contaminant level to the controller, and a downstream contaminant monitor, operably connected to and controlled by the controller and in fluid communication with the test fluid path at a position near the outlet of the test fixture, that monitors the contaminant level of fluid in the test fluid path downstream of the test fixture and reports the monitored contaminant level to the controller; a component fluid pressure monitoring system, operably connected to the controller and in fluid communication with the test fluid path near the inlet of the test fixture and near the outlet of the test fixture, that monitors the pressure change across the test fixture and reports the monitored pressure change to the controller; a pumping system, operably connected to and controlled by the controller and in fluid communication with the test fluid path, that controllably drives fluid through the test fluid path; and a system fluid flow rate measuring device, operably connected to the controller and in fluid communication with the test fluid path in substantial proximity to the test fixture, that measures the fluid flow rate through the test fixture and reports the measured fluid flow rate to the controller. The test program operates the controller to conduct a test of the test component, including controlling the operation of the hydraulic component test system in response to one or more test parameters and one or more operational parameters reported to the controller.
The operational parameters reported to the controller and used by the test program to conduct the test of hydraulic component may include the pressure change across the test fixture, the fluid flow rate through the test fixture, and the contaminant levels measured by the upstream and downstream contaminant monitors.
The test system may include a local monitor device, operably connected to the controller, that receives from the controller and displays at least one operational parameter reported to the controller and the test results reporting by the controller.
The test system may include a second location separate from the first location. The two locations are linked by a communication system, such as a telephone or the Internet. At the second location is a remote monitor device that connects to the controller via the communication system. The remote monitor device receives from the controller and displays at least one operational parameter reported to the controller. Also located at the second location is a remote input device. The remote input device connects to the controller via the communication system and conveys to the test program one or more test program parameters.
The main fluid reservoir system may include a main fluid reservoir tank support structure, connected to the main fluid reservoir tank and positioned at the first location, that supports the main fluid reservoir tank at the location. This structure may further include a first scale operably connected to the controller and positioned with respect to the first reservoir tank to measure the mass of fluid in the first reservoir tank.
The controller test program may further include a program that controls an external fluid supply flow control device to fill the main fluid reservoir tank with a predetermined amount of fluid prior to the controller conducting the test of hydraulic component. This program includes a program that orders the external fluid supply flow control device to stop the flow of fluid from an external fluid supply into the main fluid reservoir tank in response to a reported mass measurement from the first scale that indicates the amount of fluid in the in the main fluid reservoir tank has reached a predetermined amount of fluid.
The hydraulic component test system may include devices that monitor the rate of fluid flow through its contaminant monitors and a program in its controller that calculates the concentration of contaminants going into and coming out of the hydraulic component under test based on the counts of particles of contaminants in the fluid passing through contaminant monitors and the measured fluid flow rate through the monitors while also maintaining the flow of fluid through the contaminant monitors within a desired range.
To control the flow of fluid past the contaminant monitors, the hydraulic component test system may include upstream and downstream measuring fluid path flow control and flow rate measuring devices. Each of these devices include: a first capillary in fluid communication with the respective upstream and downstream measuring fluid paths and having an inlet and an outlet; a first capillary pressure monitor, operably connected to the controller and in fluid communication with the inlet and outlet of the first capillary, that measures the pressure change across the first capillary and reports the measurement to the controller; and a first controllable valve, in fluid communication with the first capillary and operably connected to and controlled by the controller, that controls the fluid flow through the first capillary. The controller test program includes a program that controls the fluid flow through the first capillaries of the upstream and downstream measuring fluid path flow control and flow rate measuring devices in response to the respective pressures reported by the associated first capillary pressure monitors. The controllable valves can be needle valves operated by stepping motors.
The pumping system the of hydraulic component test system may include a test pump that pumps fluid through the test fluid path, a hydraulic motor that drives the pump, and a hydraulic pump that connects to the hydraulic motor via hydraulic fluid lines that provides the fluid flow volume in the first hydraulic lines to drive the hydraulic motor. The hydraulic motor may be driven by a variable displacement pump having a rotor and operably connected to and controlled by the controller such that the controller can control the pitch of the rotor, thereby controlling the volume of fluid transmitted by the hydraulic pump to the hydraulic motor via the hydraulic lines and in turn controlling the rotational speed of the hydraulic motor.
In the hydraulic component test system, the contaminant injection system may include a contaminated fluid flow rate measuring device that measures the flow rate of contaminated fluid from the contaminant injection system into the test fluid path and reports the measurements to the controller. The controller test program includes a program that causes the controller to control the contaminant fluid flow control device to control the flow of contaminated fluid into the test fluid path in response to the contaminated fluid flow rate measured and reported to the controller by the contaminated fluid flow rate measuring device. The flow rate may be determined by using an integral scale to measure the mass of fluid in the contaminant tanks with respect to time, and calculating the flow rate based on the know density of the fluid. Alternatively, the flow rate may be determined using a device similar to the device that may be used to measure the fluid flow rate through the contaminant monitoring system.
The contaminant injection system may include a metering pump that the controller controls to vary the fluid flow rate from the contaminant injection system based on the measure fluid flow rate.
The contaminant injection system may include multiple contaminant injection tanks, with one tank being used to supply the test system with contaminated fluid while one or more of the other tanks are being automatically refilled with fluid and with contaminants in a predetermined amount.